Calutron



June 28, 1955 s. M. DUKE 2,712,077

CALUTRON Filed July 30, 1946 3 Sheets-Sheet l /N VEN TOR STEPHEN M. DU/E TTORNE S. M. DUKE CALUTRON `lune 28, 1955 S. M. DUKE June 28, 1955 CALUTRON 3 Sheets-Sheet 3 Filed July 50, 1946 /NL/ENTOR 5 Tgp/15N M DUKE ATroR/VEK naar? Patented .lune 28, i955 CALUTRN tephen M. Duke, Birmingham, England Application .uly 30, 1946, Serial No. 687,059

3 Claims. (Cl. Z50-41.9)

This invention relates to apparatus for scanning a beam of charged particles to determine the intensity of the beam at various points over its cross sectional area. The invention is illustrated herein as applied to a device, known as a calutron," for separating isotopes on a scale yielding commercially useful quantities of the separated material. For a complete disclosure of a calutron and its mode of operation, reference is made to the cepending application of Ernest O. Lawrence, Serial No. 557,784, led October 9, 1944, for Methods and Apparatus for Separating Materials.

As disclosed in the above-mentioned Lawrence application, a presently preferred form of the calutron comprises an evacuated tank disposed between the poles of an electromagnet so that the evacuated space within the tank is pervaded with a substantially uniform magnetic field of high ux density. Within the tank there is provided a source unit adapted to project. a beam of positive ions of a polyisotopic charge material along an arcuate path extending transversely through the magnetic eld, whereby the paths of ions of dierent mass are caused to diverge toward respective foci disposed 180 along the arcuate beam path from the source unit. A receiver, also disposed within the tank, is positioned at the 180 foci of the streams if ions of different isotopes for separately collecting the component particles of one or more of those streams.

in connection with perfection of the design of a source unit for projecting a satisfactory beam of ions and of a receiver for receiving the desired components of the transmitted beam, it is desirable to have complete data as to the nature of the beam transmitted by any particular source unit, particularly data as to the intensity of the beam at all points over its cross section in the 180 region of focus. The present invention is admirably adapted for use in obtaining such data, and the invention will be illustrated and described herein as it is employed for this purpose.

It is a general object of the invention to prov1de apparatus that will scan a beam of charged particles 1n such manner that a series of readings may be taken that represent the intensity of the beam over any desired portion of its cross section.

More specifically, it is an object of the invention to provide apparatus that will scan a beam of charged particles in such a manner that readings may be taken that represent the intensity of the beam along strips of its cross section, the apparatus being controllable so vthat the lateral spacing of these strips may be selectively varied and so that repeated readings may be taken over any given one of the strips.

Further objects and advantages of the invention will become apparent from the following detailed description of a preferred embodiment thereof specifically designed for scanning a calutron ion beam, and from the aecompanying drawings, in which:

Figure l is a horizontal sectional view of a calutron tank, showing the arrangement of the source unit and Lit) the beam scanning apparatus within the tank and the relation of the tank to the magnet, certain parts being shown somewhat schematically for simplicity.

Fig. 2 is a vertical sectional View of the beam scanning apparatus, the plane of the section being indicated by the line 2-2 in Fig. l, with the beam scanning disk rotated 90 for the purpose of showing certain details of construction;

Fig. 3 is an end elevational view of the beam scanning apparatus shown in Figs. l and 2;

Fig. 4 is a fragmentary sectional view of the beam scanning apparatus, the plane of the section being indicated by the line 4-4 in Fig. i; and

Fig. 5 is another fragmentary sectional view of the beam scanning apparatus, the plane of the section being indicated by the line 5-5 in Fig. 4.

Referring first to Fig. l of the drawings, a calutron tank 11, having a suitable pump-out conduit i2 for evacu ating the tank, is disposed between a pair of vertically spaced-apart pole pieces i3 (only one being shown) of an electromagnet adapted to create a magnetic field pervading the interior of the tank and passing upwardly therethrough. A source unit 14 is disposed within the tank 11 and is mounted at one end of a removable wall 16 of the tank for projecting an ion beam l? along an arcuate path within the tank, the path extending transversely to the magnetic iield toward the beam scanning apparatus, generally designated i8. The beam scanning apparatus 13 is mounted at the opposite end of the removable tank wail i6 from the source unit i4, in the position adjacent the 180 region of focus of the various beam components that is normally occupied by an ion receiver employed for collecting one or more or" the beam components.

Now referring to the beam scanning apparatus in detail, as shown in Figs. 2 to 5, inclusive, the apparatus comprises a main frame including a back plate 19 and a pair of side plates 2i? and 2i disposed at opposite ends of and secured to the back plate. This frame is mounted on one end of a tubular supporting shaft 22 that projects through a suitable seal 23 in the removable tank wall 16 to the exterior of the tank, where it is preferably provided with suitable mechanism 24 (indicated schematically in Fig. l) for moving the tube axially to position the beam scanning apparatus 18 at the desired point along the path of the beam i7 in the vicinity of its 180 region of focus.

A lead screw 26, having identical journal portions 27 of somewhat reduced diameter adjacent opposite ends thereof and journal portions 28 and 29 of still further reduced diameter therebeyond, is rotatably mounted on the side plates 20 and 2l. This rotatable mounting comprises a bearing 30 in the side plate Z0 that receives one ,of the journal portions 2S and a bearing 31 in the side plate 21 that receives the other journal portion 29. rI'he journal portion 2S of the lead screw 26 projects through and beyond its bearing 30 and terminates in a beveled pinion 33 that is suitably pinned or keyed thereto. The lead screw 26 is enclosed for substantially the full distance between the side plates 20 and 2l by a tube 34. Adjacent the side plate 20, the tube 34 terminates in a spur gear 36 that is coaxially secured thereto in any desired manner and has a bearing 37 centrally mounted therein for receiving the journal portieri 27 at that end of the lead screw 26. Adjacent the side plate 2l, the tube 34 terminates in an end plate 38 having a bearing 39 centrally mounted therein for receiving the journal portion 27 at that end of the lead screw 26. From the foregoing, it will be apparent that the lead screw 26 and the encompassing tube 34 are coaxially mounted for independent rotation about their common axis, the lead screw being adapted to be driven by driving the beveled gear 33 and the tube being adapted to be driven by driving the spur gear 36. l

The tube 34 has a longitudinally extending slot 41 cut through its tubular Wall for the entire length of the tube, and a hub structure, generally designated 42 is mounted for sliding movement longitudinally of the tube and is keyed thereto so as to rotate therewith by a hub portion that projects into the slot 41. Referring to the hub structure 42 in greater detail, it includes two collar portions 43 and 44 that surround the tube 34 and are secured together in a manner described hereinafter to form, in effect, a single collar. The hub structure 42 also includes two identical rings 46, each of which is provided with a radially extending lug 47. One of the rings 46 is disposed inside the tube 34 and around the lead screw 26 with its lug 47 projecting into the slot 41 and welded or soldered at 48 to the outer collar portion 43 of the hub structure 42. The other of the rings 46 is similarly disposed inside the tube 34 with its lug 47 projecting into the slot 41 and welded or soldered at 49 to the outer collar portion 44 of the hub structure 42.

A traveler block 51, having a graphite bushing 52 mounted therein and internally threaded to match the thread of the lead screw, is disposed inside the hub structure 42 between the rings 46 and surrounds the lead screw in threaded engagement therewith. The traveler block 51 is provided with a lug 53 projecting into the slot 41, whereby rotation of the lead screw 26 and the tube 34 in different directions, or in the same direction at different speeds, causes the traveler block to rotate at a different rate than the lead screw and, as a result, to translate in one direction or the other along the lead screw. When the traveler block 51 moves along the lead screw, the hub structure 42 is constrained by the rings 46 to move therewith.

A hollow disk structure, generally designated 55,` is mounted on the hub structure 42 coaxially therewith. The disk structure comprises a pair of identical, spacedapart disks 56 having an annular ring 57 of the same outside diameter as the disks 56 sandwiched between the disks around their entire peripheries; the assembly being held together by suitable fastening elements 58. The disks 56 are centrally apertured, and the inner periphery of one of them is secured between the outer collar portions 43 and 44 of the hub structure 42 by fastening elements 59, while the inner periphery of the other disk 56 is secured to the outer collar portion 44 of the hub structure by fastening elements 60. A single aperture 62 is formed in the ring 57 and extends radially inwardly therethrough from the outer peripheral surface thereof. The aperture 62 is preferably flared laterally from its outer end toward its inner end so that the opening in the outer periphery of the ring is detined by a sharp edge 63.

An electrode structure is disposed inside the hollow disk structure 55 in such a position that it will intercept all particles traveling radially into the disk structure through the aperture 62. This electrode structure comprises an electrically conducting rod 65 having an annular flange 66 formed integrally thereon and a tubular insulator 67 surrounding the rod 65 and held against the flange 66 by a cup member 68 and a nut 69 that is contained within the cup member and is threaded onto one end of the rod. A split collar 71 is clamped around the insulator 67 and is secured to one of the disks 56 by a pair of fastening elements 72, whereby the electrode structure is positioned with the cup member 68 disposed directly behind the aperture 62 for receiving particles passing therethrough. The electrically conducting rod 65 of the electrode structure extends radially toward the hub structure 42 and projects into an aperture 73 formed in the outer collar portion 44 thereof, terminating short of the surface of the tube 34.

In order to conduct current to the electrode structure as required to neutralize charged particles intercepted thereby, the end plate 38 of the tube 34 has an insulating ring 75 of a material such as Bakelite secured thereto and surrounding the adjacent end of the tube 34. The insulating ring 75 has a copper strip 76 inlaid into its outer surface for a portion of its perimeter to either side of the slot 41 in the tube 34, and a pair of commutator brushes 77, carried by a spring 78, are mounted to bear against the outer periphery of the ring 75 so as to contact and ride over the copper strip each time the tube 34 makes a complete turn about its axis of rotation. The spring 78 is carried in an insulating bracket 79 formed of a material such as Lai/ite and secured to the end plate 21 by suitable fastening elements. The inlaid copper strip 76 is electrically connected to the conducting rod 65 of the electrode structure by an insulated conductor 81 formed of a resilient electrically conducting material and coiled a number of times about the lead screw 26, inside the tube 34, so as to form a helical spring. One end of this conductor 81 extends beyond one end of the helical portion thereof and passes through an aperture 82 formed in one of the ring portions 46 of the hub structure 42. From the aperture 82, this end of the conductor 81 passes partially around the interior of the hub structure 42 and is soldered to the innermost end of the electrically conducting rod 65. The opposite end of the conductor 81 extends from the helical portion thereof through the slot 41 in the tube 34 and is soldered to one edge of the inlaid copper strip 76. An electrical lead 83 is connected at one end to the commutator brushes 77 and at its opposite end to a conductor plug 84 that projects through the removable tank 16 and is provided with a tap on the outside of the tank to which a suitable meter (not shown) may be connected, the meter being connected to ground in a well known manner for permitting current to ilow therethrough and ultimately t0 the electrode structure.

Since the disk structure 55, the hub structure 42, the tube 34, and the end plate 38 of the tube all rotate together, there is no relative rotation of the electrode structure and the inlaid copper strip 76 between which the conductor S1 extends. The helical portion of the conductor 81 is capable of being extended the same as any helical spring, thereby permitting the disk structure to move along the axis of the various rotating parts without disrupting the electrical connection between the electrode structure and the inlaid copper strip.

Metal shields and 85, of any suitable shape, are preferably respectively mounted on the side plates 20 and 21 for shielding the mechanisms at the two ends of the tube 34 from ion bombardment. This is desirable to prevent these mechanisms from being coated with scattered beam particles or eroded as a result of direct bombardment by the beam.

In order to drive the tube 34 about its axis of rotation at a desired speed, the spur gear 36 at one end of the v tube 34 is engaged by a spur pinion 86 that is keyed to a rotatable idler shaft 87, the idler shaft being rotatably mounted at one end in a suitable bearing 88 carried by a bearing support 89, which is in turn mounted on the adjacent side plate 20 of the beam scanner frame. The opposite end of the idler shaft 87 projects through and beyond a suitable bearing 91 mounted in the side plate 20 and terminates in a beveled gear 92, that is suitably pinned or keyed thereto, whereby rotation of the beveled gear 92 will cause rotation of the tube 34.

The beveled gear 33 through which the lead screw 26 is driven and the beveled gear 92 through which the tube 34 is driven are respectively associated with independent driving mechanisms that are powered by separate motors preferably mounted on the removable tank wall 16 on the outside of the tank. The driving mechanism for the beveled gear 92 comprises a beveled gear 93 that is keyed on one end of a rotatable shaft 94. The shaft 94 is journaled adjacent the beveled gear 93 in a suitable bearing 96 carried by a bracket 97 mounted on the adjacent side plate 20, and the shaft extends through a vacuum seal 98 in the removable tank wall 16. Outside the tank, the shaft 94 is operatively connected to an electric motor 99 or the like that may be mounted in any desired manner on the removable tank wall 16. The driving mechanism for the beveled gear 33 is similar to that just described and comprises a beveled pinion 101 that is keyed on one end of a rotatable shaft 102. The shaft 102 is journaled adjacent the beveled pinion 11 in a suitable bearing 103 carried by the bracket 97, and this shaft extends through a vacuum seal 164 in the removable tank Wall 16. Outside the tank, the shaft 102 is operatively connected to an electric motor 166 or the like that may be mounted in any desired manner on the removable tank wall 16. The shaft 94 and the shaft 1%.?. are both preferably provided with universal joints 107 at convenient points along their lengths for compensating for any rnisalignment of the driving mechanisms just described, and are also provided with extensible joints 198 that permit the beam scanning mechanism to be moved toward or away from the removable tank wall 16 by axial movement of the tubular supporting shaft 22, for the purpose mentioned above, without interfering with the driving mchanisms just described.

The motor 99 for driving the tube 34 is preferably a synchronous electric motor adapted to drive the tube at a constant selected speed, whereas the motor 106 for driving the lead screw 26 is preferably a D. C. shunt motor that will permit the speed at which the lead screw 26 is driven to be selectively varied and its direction of rotation to be reversed. With such motors employed for independently driving the lead screw 26 and the tube 34, the screw and tube may be caused to rotate at ditterent speeds with the ditlcrence in their 'rates of rotation selectively variable, whereby the disk structure 5S may be caused to rotate about its axis of rotation at a selected constant speed while moving along its axis of rotation at a selectively variable speed within a predetermined range from zero to a substantial figure dependent upon the maximum speed of the D. C. motor 106. Also, the disk structure 55 may be caused to move in either direction along its axis of rotation depending upon the direction of rotation of the D. C. motor 106.

The position of the slot 41 in the tube 34, the position of the aperture 62 in the disk structure 55, and the length of the inlaid copper strip 76 are so chosen that the commutator brushes 77 contact the inlaid copper strip 76 during any selected portion of the time during each revolution of the tube 34 when the aperture 62 is exposed to the beam 17. Thus, current to the electrode structure disposed behind the aperture 62 may be read during that selected time, which current Will be a direct measure of the intensity of that portion of the beam scanned by the aperture'62. If the speeds of rotation of the motors 99 and 106 are such that the disk structure 55 is moving along its axis of rotation, a series of current readings will be obtained that represent the intensity of the beam along strips of its cross-section that are unrforrnly spaced across the width of the beam. If the speeds of rotation of the motors 99 and 106 are s uch that the disk structure 55 is not moving in an axial direction, the successive current readings will be repeated indications of the intensity of the beam along the same cross-sectional strip. if the disk structure 55 is caused to move sutliciently slowly, the successive strips along which readings are taken be caused to overlap to any degree desired.

From the foregoing description, it will be apparent that l have provided apparatus admirably adapted to give complete and valuable data as to the intensity of a beam of charged particles over its entire cross-sectional area or over selected narrow strips of its cross-sectional'area. While the invention has been illustrated by an embodiment thereof specially designed for studying a calutron ion beam, it will be appreciated that it is adapted to be used for studying other types of beams of charged particles, and the invention is not intended to be limited to use for studying a calutron ion beam. Also, while a specific embodiment 'of the invention has been disclosed in detail, it will be understood that this has been done for illustrative purposes and that the invention is not limited to those details except as required by the true spirit and Scope of the appended claims.

What is claimed is:

l. Apparatus for scanning a beam of charged particles, comprising an electrode, means supporting said electrode for rotation about and translation along an axis adapted to be positioned in the path of a beam to be scanned so that it extends transversely across the beam, means for rotating the electrode about said axis at a predetermined speed, means for moving the electrode along said axis at a selected speed, and means for reading current to said electrode.

2. Apparatus for scanning a beam of charged particles, comprising an electrode, means supporting said electrode for rotation about and translation along an axis adapted to be positioned in the path of a beam to be scanned Y so that it extends transversely across the beam, means for rotating the electrode about said axis at a predetermined speed, means for moving the electrode along said axis at a selected speed, means shielding said electrode from bombardment by particles traveling in a beam to be scanned While the electrode is moving along a predetermined portion of its path about said axis While leaving it exposed to such bombardment during the remainder of its travel about said axis, and means for reading current to said electrode.

3. Apparatus for scanning a beam of charged particles, comprising an electrode, means supporting said electrode for rotation about and translation along an axis adapted to be positioned in the path of a beam to be scanned so that it extends transversely across the beam, means for rotating the electrode about said axis at a predetermined constant speed, means for moving the electrode along said axis at a selectively variable speed, means shielding said electrode from bombardment by particles traveling in a beam to be scanned while the electrode is moving along a predetermined portion of its path about said axis while leaving it exposed to such bombardment during the remainder of its travel about said axis, and means for reading current to said electrode.

No references cited. 

1. APPARATUS FOR SCANNING A BEAM OF CHARGED PARTICLES, COMPRISING AN ELECTRODE, MEANS SUPPORTING SAID ELECTODE FOR ROTATION ABOUT AND TRANSLATION ALONG AN AXIS ADAPTED TO BE POSITIONED IN THE PATH OF A BEAM TO BE SCANNED SO THAT IT EXTENDS TRAVERSELY ACROSS THE BEAM, MEANS FOR ROTATING THE ELECTRODE ABOUT SAID AXIS AT A PREDETERMINED SPEED, MEANS FOR MOVING THE ELECTRODE ALONG SAID AXIS AT A SELECTED SPEED, AND MEANS FOR READING CURRENT TO SAID ELECTRODE. 